Manufacture of alkyllead compounds



Patented June 26, 1951 MANUFACTURE OF ALKYLLEAD COMPOUNDS GeorgeCalingaert, Geneva,

N. Y., and Hymin Shapiro, Detroit, Mich, assignors to Ethyl Corporation,New York, N

Delaware Y., a corporation of No Drawing. Application July 27, 1950,Serial No. 176,251

This invention relates to a new process for making alkyllead andaryllead compounds.

The most important of the alkyllead compounds is tetraethyllead which ismade commercially by reacting monosodium-lead alloy with ethyl chloridein accordance with the following equation This process has beensuccessful but it has certain disadvantages among which are the 11609"-sity of forming a sodium-lead alloy and the inherent limitations inyield since three-fourths of the lead is not utilized in the reaction.The unused lead must be recovered and re-alloyed with the sodium. Theusual yield of tetraethyllead is about 22 weight per cent based on thelead.

One object of our invention is to provide a process for increasing theyield of tetraethyllead obtained in the present process. Another objectis to provide a process using free lead, thus avoiding the expensivealloying operation.

The above objects are accomplished by reacting an alkylating orarylating agent with lead and an aryl or alkyl lithium compound. Ourreaction can be generalized by the following equation:

where R is an alkyl or aryl radical and X is an inorganic acid radicalwhich forms a salt with the lithium.

It should be noted that the theoretical yield of the alkyllead compoundbased on the lead is four times that of the present commercial process.

Any of the alkylating agents heretofore used.

or described in the prior art can be used, among which are the alkyl andaryl halides preferably the iodides, bromides and chlorides, the dialkylsfilfates and the trialkyl phosphates. In general, t e alkylating andarylating agents are esters of inorganic acids having the proper alkylgroups for making the desired alkyllead compound, and having aninorganic acid group which forms a salt with the lithium. Among thosewhich can be used in our invention are the ethyl, propyl, butyl andphenyl chlorides, as well as the corresponding bromides and iodides,diethylsulfate and triethylphosphate.

Catalysts, while not essential to our invention, do improve the yields.The preferred catalysts are the dialkyl ethers such as dimethyl,diethyl, and diisopropyl ethers. Also catalysts of the amine type suchas trimethylamine, diethylamine and triethylammonium iodide can be used.

5 Claims. (Cl. 260-437) While tetraethyllead is the principal compounddiscussed herein because of its large commercial use, other alkylleadcompounds such as tetramethyllead, tetrapropyllead, dimethyldiethyllead,methyltriethyllead, tetraphenyllead, diethyldiphenyllead can be made bythe process of our invention.

Various alkyl or aryl lithiums can be used depending on the lead alkyldesired such as the methyl, ethyl, propyl, butyl and phenyl lithium. Ifthe alkyl group attached to lithium is different than the one attachedto the alkylating agent, a mixture of alkyllead compounds usuallyresults.

For best results a slight stoichiometric excess of the alkyl lithiumshould be used although lesser amounts give proportionate yields andwill result in an increase in yield when used concurrently with thepresent process.

The temperature employed is not important, the preferable range being 50and C. The pressure used is not critical but should be sufficient at thetemperature employed to maintain the alkylating agent in the liquidphase. The time of reaction is between about 30 minutes and 5 hours. Theamount of alkylating agent employed is not critical but an excess overthe stoichiometric amount required in the above general equation ispreferred.

Our process can be used concurrently to improve the yield of the presentcommercial process or it can be used independently in treating theunreacted lead from the present process or other forms of free lead. Byconcurrently is meant either adding the alkyllithium along with theother reactants to the present process or first conducting the reactionof the present process and then adding the alkyllithium together withadditional alkylating agent, if required. Such an overall reaction isexpressed by the following illustrative equation:

Also, in place of sodium other metals, generally the alkali earth andalkali metals, well known for this purpose, can be alloyed with the leadand used in the above reaction among which are potassium and calcium.

Our invention can best be understood by referring to the followingtypical working examples in which all the parts and percentages are byweight.

Example I Two-stage reaction using sodium-lead alloy and ethyl chloride:A charge of 100 parts of NaPb alloy is added to a reaction vessel,equipped with an agitator, a jacket for circulation of heating orcooling liquids, a reflux condenser, charging and discharging ports,liquid feed lines, and means for releasing the pressure. Liquid ethylchloride in the amount of 112 parts is added under pressure to thestirred solids in the vessel over a period of one-half hour. Bycontrolling the flow of liquid in the autoclave jacket and in the refluxcondenser the temperature of the reaction mass is permitted to rise froman initial temperature of 50 C. to a temperature of 70 C. during thisfeed period. The pressure in the autoclave during this feed rises to 75pounds per square inch gauge where it is maintained. The temperature ofthe stirred reaction mixture is maintained at 70 C. for an additional 15minutes maintaining the 75 pound pressure. For the second stage, anadditional quantity of 56 parts of ethyl chloride which has beenpremixed with 19.1 parts of ethyl lithium, is added uniformly. underpressure as a slurry to the autoclave over a period of 15 minutes, againmaintaining the 75 pounds pressure. The temperature of the stirredreaction mass is maintained at 70 C., while maintaining 75 poundspressure, for an additional 85 minutes. At the end of this period thepressure in the autoclave is reduced to atmosperic by venting for a 15minute period at 70 C. Nitrogen is passed over the reaction mass whilethe autoclave is open to the atmosphere. The mass is then cooled to 45C. over an additional 30 minute period while flushing with a stream ofnitrogen. The reaction mass is then discharged slowly to a steam-stillcontaining 250 parts of water. With 100-steam fed to the jacket of thesteam-still, 1a forecut of ethyl chloride is taken, up to a, vaportemperature of 70 C. At this point the steam jets are then turned on,and with the jacket steam off, the tetraethyllead is distilled for oneand one-half hours after the first drop of tetraethyllead appears in thedistillation receiver. The yield of product is 92.9 parts, or a yield of66.2 per cent based on the lead present in the sodium-lead alloy.

Example H In an operation similar to Example 1 above, in the secondstage the additional ethyl chloride was added along with 21.7 parts ofethyl lithium and 70 parts of diethyl ether. The product was recoveredas in the foregoing example. The amount of alkyllead produced in the twostages of this operation was 119.5 parts or 85 per cent based on thelead present in the sodium-lead alloy employed in the first stage.

4 Example III In the same equipment described in Example I, parts oflead recovered from an operation similar to that described as the firststage of Example I was treated with 198 parts of ethyl chloride premixedwith 37.5 parts of ethyl lithium and 117 parts of diethyl ether. Thereaction was conducted. in the same manner as in the second stage ofExample I. The product obtained in this reaction was 139.5 parts ofalkyllead, corresponding to a yield of 89.5 per cent based upon the leadcharged to the reactor.

Thus, a fourfold increase in yield over that obtained in the presentcommercial process is made byour process.

Other embodiments of this invention can be made without departing fromthe spirit and scope of our invention which is not limited to specificembodiments given herein.

We claim:

1. A process for making hydrocarbon-lead compounds comprising reactinglead with a reagent selected from the class consisting of arylating andalkylating agents which include the hydrocarbon radical in question andhave a negative radical which reacts with lithium, and with ahydrocarbon-lithium compound in which the hydrocarbon radical isselected from the group consisting of alkyl or aryl.

2. A dual process for making tetraethyllead which comprises reacting asodium lead alloy with ethyl chloride, and reacting the free leadso-produced with ethyl chloride in the presence of ethyl lithium anddiethyl ether.

3., The process of claim 1 in which the hydrocarbon-lithium compound isan alkyl lithium.

4. The process of claim 1 for making tetraethyllead in which thealkylating agent is an ethylating agent and the hydrocarbon lithiumcompound is ethyl lithium.

5. The process of claim 1 for making tetraethyllead in which thealkylating agent is ethyl chloride, the hydrocarbon lithium compound isethyl lithium, and further the process is conducted in the presence ofethyl ether as a catalyst.

GEORGE CALINGAERT. HYMIN SHAPIRO.

Name Date Groll Dec. 5, 1933 Number

1. A PROCESS FOR MAKING HYDROCARBON-LEAD COMPOUNDS COMPRISING REACTINGLEAD WITH A REAGENT SELECTED FROM THE CLASS CONSISTING OF ARYLATING ANDALKYLATING AGENTS WHICH INCLUDE THE HYDROCARBON RADICAL IN QUESTION ANDHAVE A NEGATIVE RADICAL WHICH REACTS WITH LITHIUM, AND WITH AHYDROCARBON-LITHIUM COMPOUND IN WHICH THE HYDROCARBON RADICAL ISSELECTED FROM THE GROUP CONSISTING OF ALKYL OR ARYL.